The present invention relates to a method, and also to a system, for monitoring the condition of a plurality of electrical devices. The invention is particularly applicable for monitoring the condition of a plurality of electrical switching devices, such as those operated by sensors, and for determining the location of a malfunctioning device; and the invention is therefore described below with respect to this application.
Switching type sensors for detecting various conditions are commonly used in a wide variety of applications, such as intrusion-detecting systems and fire alarm systems. For example, intrusion-detecting systems frequently use electrical switches for detecting the opening of a door or window. Such systems are commonly equipped with means, such as a continuity detector, to enable the user to determine the condition of all the devices, i.e., whether the switches are all closed. However, the known systems do not usually enable the user to detect whether all of the sensors are functioning properly, i.e., are not shorted, opened or bypassed, or the location of an open or malfunctioning sensor.